Dendritic molecules are repeatedly branched species that are characterised by structural perfection. This is based on the evaluation of both symmetry and polydispersity. The field of dendritic molecules can roughly be divided into low-molecular weight and high-molecular weight species. The first category includes dendrimers and dendrons, and the second includes dendronised polymers, hyperbranched polymers and brush-polymers (called also bottle-brushes).
The first dendrimers were synthesised divergently by Vögtle in 1978 (see, e.g., Buhleier, et al., Synthesis 1978: 155-158; herein incorporated by reference in its entirety), by Denkewalter as polylysine dendrimers in 1981 (see, e.g., U.S. Pat. No. 4,289,872 and U.S. Pat. No. 4,410,688; each herein incorporated by reference in their entireties), by Tomalia in 1983 (see, e.g., U.S. Pat. No. 4,507,466) (see, e.g., Tomalia, et al., Polymer Journal 1985 17:117; each herein incorporated by reference in their entireties), and by Newkome in 1985 (see, e.g., Newkome, et al., 1985 J. Org. Chem. 50: 2003; herein incorporated by reference in its entirety). In 1990 a convergent synthesis method was introduced by Fréchet (see, e.g., Hawker, et al., 1990, J. Am. Chem. Soc. 112: 7638; herein incorporated by reference in its entirety). Dendrimers then experienced an explosion of scientific interest because of their unique molecular architecture. This resulted in more than 5,000 scientific papers and patents published by the end of 2005.
Polyamidoamine (PAMAM) dendrimers are a common class of dendrimers suitable for many materials science and biotechnology applications. PAMAM dendrimers consist of alkyl-diamine core and tertiary amine branches. They are available in generations G 0-10 with 5 different core types and 10 functional surface groups. Methods for synthesizing PAMAM dendrimers, however, have limitations. For example intramolecular dendrimer polymerization, intermolecular looping, and dendrimers having missing branches are common problems associated with classical synthesis methods. Accordingly, there exists a need for improved methods for synthesizing PAMAM dendrimers.